The present invention relates to a thermal spraying powder containing granulated and sintered particles of an yttrium-aluminum double oxide.
In a semiconductor manufacturing technique, as the requirement for the enhanced speed of semiconductor devices is increased, finer patterns have been developed. In particular, in the etching technique, wet etching that utilizes an acid or alkaline solvent is shifted to dry etching for higher machining accuracy. Specifically, a technique that has been widely used in manufacture of semiconductor components such as LSI is a technique for forming fine patterns through dry etching of gas plasma that uses a halogen based gas such as fluorine and chlorine.
In general, most of members of semiconductor manufacturing apparatuses are formed of metal such as stainless-steel and aluminum, and have low plasma erosion resistance, but members that have a risk of being eroded by plasma are formed of oxide ceramics such as alumina and yttria to avoid plasma erosion. As the diameters of silicon wafers are increased, the sizes of the semiconductor manufacturing apparatuses have been increased. Accordingly, the sizes of members of semiconductor manufacturing apparatuses have been increased. However, bulk oxide ceramics is difficult to machine and the manufacturing cost is high. Therefore, large-size members that have a risk of being eroded by plasma, in particular, are formed not of the bulk oxide ceramics, but of metal base material provided with an oxide ceramics coating on its surface.
Takao KITAGAWA et al. disclosed, in an article entitled “Evaluation for Plasma Resistance of Ceramics” on pages 17 to 22 in Sumitomo Osaka Cement Technical Report 2004 edition published on Dec. 15, 2003, that an yttrium-aluminum double oxide such as yttrium aluminum garnet (YAG) as well as oxide ceramics such as alumina has high plasma erosion resistance. However, bulk double oxide ceramics disclosed in the article is difficult to machine and the manufacturing cost is high like the bulk yttria and bulk alumina.
A plasma spraying method is well known as a technique for manufacturing coatings made of oxide ceramics and double oxide ceramics. The plasma spraying method is advantageous in that the speed for manufacturing a coating is faster than those of the physical vapor deposition method and the chemical vapor deposition method, and that the base material is not restricted. Furthermore, since the physical vapor deposition method and the chemical vapor deposition method need to be performed under vacuum or reduced pressure, or in an ambient atmosphere in which the composition of gas is controlled, the physical vapor deposition method and the chemical vapor deposition method must be performed in a stainless-steel or glass container to form a coating. Contrastingly, a coating can be formed in the atmospheric air with the plasma spraying method, and there are hardly any restrictions like those of the vapor deposition methods.
The thermal spraying powder is generally fed from a powder feeder to a spray gun through a thin powder tube having an inner diameter of a few millimeters. Therefore, in view of feeding the thermal spraying powder in a stable manner avoiding clogging of the powder tube, it is quite important that the thermal spraying powder has sufficient flowability. In this respect, since granulated and sintered particles having spherical shapes have sufficient flowability as compared to fused and crushed particles and sintered and crushed particles, the granulated and sintered particles are suitable for the thermal spraying powder.
Since the yttrium-aluminum double oxide has a relatively high melting point, there is a risk that the double oxide could be insufficiently fused by the spraying flame when used as the thermal spraying powder. However, in view of spraying the thermal spraying powder at high deposit efficiency, it is quite important that the thermal spraying powder is reasonably easily fused. In this respect, since each of the granulated and sintered particles is formed by granulating and sintering raw-material particles and therefore has appropriate gaps between the granulated and sintered raw-material particles, the granulated and sintered particles are reasonably easily fused as compared to the fused and crushed particles and the sintered and crushed particles. Thus, the granulated and sintered particles are suitable for the thermal spraying powder. The granulated and sintered particles are also suitable for the thermal spraying powder in that there is less risk of contamination by impurities during manufacture as compared to the fused and crushed particles and the sintered and crushed particles.
As described above, since the granulated and sintered particles are suitable for the thermal spraying powder, a technique for plasma spraying the granulated and sintered particles of the yttrium-aluminum double oxide as disclosed in Japanese Laid-Open Patent Publication No. 2002-80954 is useful as a technique for forming a thermal spray coating of the yttrium-aluminum double oxide. However, there is yet room for improvements in the technique disclosed in Japanese Laid-Open Patent Publication No. 2002-80954 in that the design idea for reliably forming the thermal spray coating is insufficient.